How to Replace a Rocker Box Gasket on a 1200 Harley Sportster

Kyle McBrideUpdated April 17, 2017

The 1,200cc Harley-Davidson Sportster XL and XR models come equipped with a two-piece, aluminium rocker-box cover assembly that houses the rocker arms, valve stems and upper pushrod ends. Engine oil is pumped up to the rocker boxes, where it lubricates the top-end components before being evacuated by the oil scavenging system. High mileage and extreme conditions cause the gaskets in the rocker boxes to fail and create a potentially serious oil leak. The rocker box gaskets can be replaced with specialised tools and basic mechanical skills.

Place the fire extinguisher close at hand. Don safety glasses.

Open the left side cover located below the seat, on the left side of the bike, by hand. Remove the fuel pump fuse from the fuse panel with a fuse puller.

Start the engine with the ignition key. Allow the engine to run until it stalls and dies. Turn the engine over with the ignition key to purge any remaining fuel from the lines.

Turn off the ignition and reinstall the fuel pump fuse in the fuse panel, by hand. Remove the main fuse from the panel with a fuse puller to prevent accidental starting of the engine.

Lift up on the quick-release sleeve on the fuel hose from the point where it exits the fuel tank, then gently pull down on the fuel hose to separate it from the fuel tank. Clean up any spilt fuel with a clean shop rag.

Remove the fuel filler cap from the fuel tank. Insert the fuel transfer pump's pickup hose into the fuel tank while holding the bike vertical on level ground. Lead the fuel transfer pump discharge hose into a clean container, approved for gasoline storage. Pump the fuel tank empty.

Remove the forward and rear fuel tank mounting bolts from the bike with an Allen driver, ratchet and wrench. Lift the fuel tank off the bike and store in a safe area. Cover the fuel tank with clean shop rags or with a clean blanket to protect the paint.

Lift the bike with a bike lift, so that the rear wheel is off the ground. Ensure that the bike is stable and secure on the lift before proceeding.

Remove the four outer rocker box-cover screws and sealing washers from each rocker box, using an Allen driver and ratchet. Lift the outer rocker box covers from the engine. Discard the used sealing washers and the rubber rocker box seal.

Place the transmission in first gear with the shift lever. Rotate the rear wheel forward, by hand, until both valves on the rear cylinder are closed.

Remove the two small screws on the spark plug side of the rocker box with a wrench. Remove the three bolts and washers with a wrench.

Remove the four rocker-arm retainer bolts, in a cross pattern, using a wrench. Loosen each bolt 1/4 of a turn, until the pressure from the valve springs is released. Lift the inner rocker box from the engine. Remove the inner rocker-box gaskets with a gasket scraper. Repeat steps 3, 4 and 5 for the front cylinder.

Place the new inner rocker-box gasket onto the front cylinder head, with the gasket bead facing up. Place the inner rocker-box cover onto the head and start the four rocker-arm retainer bolts by hand. Torque the rocker-arm retainer bolts to 8.16 to 9.98kg-ft of torque in a cross pattern, using a torque wrench and socket. Tighten each bolt 1/4 of a turn, until the target torque is met.

Rotate the rear wheel forward until the rear cylinder pushrods are in the down (or valve closed) position. Repeat step 1 on the rear cylinder.

Install and torque the three bolts in each of the inner rocker boxes to 61.2 to 70.3kg-in with a torque wrench and socket. Install and torque the two screws in each inner rocker box to 61.2 to 70.3kg-in with a torque wrench and socket.

Place the rocker-box rubber seal into its groove on the top edge of the inner rocker box. Place the outer rocker-box cover in position on top of the inner rocker box.

Place a new sealing washer onto each rocker cover screw. Start the four screws in each rocker cover by hand. Check the rubber seal and ensure that it is still in the groove before proceeding. Torque the rocker cover screws to 54.4 to 76.2kg-in with a torque wrench and Allen driver.

Position the fuel tank onto the frame and install the fuel tank mounting bolts by hand. Torque the fuel tank mounting bolts to 6.8 to 9.07kg-ft with a torque wrench, Allen driver and wrench.

Push up on and hold the quick-release fuel line connector by hand. Push the fuel line up onto the fuel pump nipple, then pull down on the quick-release to snap it into position.

Reinstall the main fuse in the fuse panel, by hand. Close the left side cover.

Lower the bike off the bike lift and rest it on the jiffy stand. Refill the fuel tank. Start the engine and observe the rocker box areas for leaks before driving the bike.

Warning

Use caution when dealing with gasoline. Perform the tank draining procedure in an open area, with ample fresh air and away from any sources of ignition such as sparks, open flame or cigarettes. If any part of the procedure seems beyond your capabilities, consult a qualified Harley-Davidson technician before proceeding.